1. Field of the Invention
This invention relates to the automation of a twisting plant for producing synthetic fiber yarn, and more particularly, to a system for conveying packages of synthetic fiber yarn to convey them to and from a twisting machine.
2. Prior Art
Reference is first made to FIG. 10 illustrating the basic flow of synthetic fiber yarn in a twisting plant. A twisting machine 101 twists raw yarns or unfinished yarns to form packages of processed yarns. "Full" means full packages of unfinished yarns or processed yarns, and "empty" means take-up tubes. Packages of unfinished yarns are packed in boxes, and the boxes are conveyed on pallets from a raw yarn plant to an unpacking device 102 by which they are opened, and the packages are conveyed to a package exchange robot 104 by a package conveying apparatus 103. The packages are transferred from the package exchange robot 104 to the desired positions in the twisting machine 101. The take-up tubes left empty after processing are conveyed to a receptacle 105 for empty take-up tubes by the package exchange robot 104 and the package conveying apparatus 103. The packages of processed yarns leaving the twisting machine are doffed by an automatic doffer 106, and conveyed to a stocker 108 by a yarn conveying apparatus 107. They are inspected at 109 and packed at 110 for shipment. Although the twisting machine 101 is operated on a 24-hour-a-day basis, the inspection 109 and the packing 110 are usually performed on an 8-hour-a-day basis, and the stocker 108 is, therefore, provided as an accumulator therebetween. Take-up tubes are supplied from a take-up tube supplying apparatus 111 to the twisting machine 101 through the yarn conveying apparatus 107 and the automatic doffer 106.
The package conveying apparatus 103 and yarn conveying apparatus 107 which are employed have a critical bearing on the efficiency of such a flow in a limited space. It is usual to employ a tray conveyor, a pin truck, or an overhead conveyor. The arrangement of machines and apparatuses in a twisting plant in which an overhead conveyor is employed will be described with reference to FIG. 11. The overhead conveyor is shown at 120 in FIG. 11, and serves as both the unfinished yarn and processed yarn conveying apparatuses, and the machines and apparatuses are arranged along it. They are twisting machines 1A to 1N, creels 2, package exchange robots 4 associated with the creels 2, rotary pegs 5, automatic doffers 6 associated with the rotary pegs 5, a tray stocker 121, an inspection apparatus 7 provided along a tray conveyor, a packing apparatus 8, an apparatus 9 for collecting empty take-up tubes, an apparatus 10 for supplying take-up tubes, and an unpacking apparatus 11.
Description will be made with reference to FIG. 12 of a station A for delivering packages from the unpacking apparatus 11 to the overhead conveyor 120. Packages P of unfinished yarns are transferred from unpacked pallets 12 to a lift 123 by a transfer robot 122, and from the lift 123 to hangers 120a attached to the overhead conveyor 120. The hangers 120a which have received packages P are turned by 180.degree. by turning cams 120b.
Description will now be made with reference to FIG. 13 of a station B for transferring packages P from the overhead conveyor 120 to the package exchange robot 4. The package P is transferred from the hanger 120a to an arm 124a on a lift 124, and the arm 124a is lowered and turned by 90.degree. so as to face the robot 4. The robot 4 travels and receives the package P.
Description will now be made with reference to FIGS. 14(a, b)of a station C for delivering packages of processed yarns from the rotary peg 5 of a twisting machine to the overhead conveyor 120. Packages P of processed yarns are transferred one by one from the rotary peg 5 to an arm 125a on a lift 125, and the arm 125a is raised and turned by 90.degree. to deliver the packages P one by one to the hangers 120a.
Description will now be made with reference to FIG. 15 of a station D for delivering packages P of processed yarns from the overhead conveyor 120 to the tray stocker 121. The package P is transferred from each hanger 120a to a lift 126 and its arm 126a is lowered. A transfer robot 127 receives the package P from the arm 126a, and puts it in a tray 13 on the conveyor 121a leading to the tray stocker.
The system for conveying packages of synthetic fiber yarn by employing an overhead conveyor as hereinabove described is designed for conveying packages one by one to and from the twisting machines, and has, therefore, the drawback of having only a limited capacity and being suitable for use with only a limited number of twisting machines. Although a pin truck may be useful for conveying a large number of packages at a time, a sufficiently large floor space is required for an operatorless carriage to travel to move the pin truck, and moreover, the transfer of packages to and from the pin truck produces a great burden. A tray conveyor can diminish such burden, but requires a large floor space for installation.